// base64.ts
export class Base64 {
  _keyStr = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/='

  encode(input: string) {
    let output = ''
    let chr1, chr2, chr3, enc1, enc2, enc3, enc4
    let i = 0
    input = this._utf8_encode(input)
    while (i < input.length) {
      chr1 = input.charCodeAt(i++)
      chr2 = input.charCodeAt(i++)
      chr3 = input.charCodeAt(i++)
      enc1 = chr1 >> 2
      enc2 = ((chr1 & 3) << 4) | (chr2 >> 4)
      enc3 = ((chr2 & 15) << 2) | (chr3 >> 6)
      enc4 = chr3 & 63
      if (Number.isNaN(chr2)) {
        enc3 = enc4 = 64
      }
      else if (Number.isNaN(chr3)) {
        enc4 = 64
      }
      output
        = output
          + this._keyStr.charAt(enc1)
          + this._keyStr.charAt(enc2)
          + this._keyStr.charAt(enc3)
          + this._keyStr.charAt(enc4)
    }
    return output
  }

  _utf8_encode(str: string) {
    str = str.replace(/\r\n/g, '\n')
    let utftext = ''
    for (let n = 0; n < str.length; n++) {
      const c = str.charCodeAt(n)
      if (c < 128) {
        utftext += String.fromCharCode(c)
      }
      else if (c > 127 && c < 2048) {
        utftext += String.fromCharCode((c >> 6) | 192)
        utftext += String.fromCharCode((c & 63) | 128)
      }
      else {
        utftext += String.fromCharCode((c >> 12) | 224)
        utftext += String.fromCharCode(((c >> 6) & 63) | 128)
        utftext += String.fromCharCode((c & 63) | 128)
      }
    }
    return utftext
  }
}

export default Base64
